I was wondering about the depth of the vagina. I've read statistics that say that the average vagina is only 3 to 4 inches deep. This seems way too small to me, since the average penis is considerably longer than that. Wouldn't that mean that most penises would crash into the cervix repeatedly during intercourse? Since this obviously doesn't happen, my question is this: does the vagina actually elongate during intercourse to accommodate the entire length of the average penis?

Dear Alice, 

I take Valtrex daily to protect me from cold sores I get on my face. I haven’t had one since I started taking it a few years ago. My partner gets cold sores on his mouth and has recently performed oral sex on me while having a cold sore. Will the daily Valtrex protect me from developing genital herpes? How will this affect me in the future?

What are the risks of HIV infection for the passive partner of oral sex?

If one has a long-term partner and neither AIDS nor any other STD is a concern, is there any medical reason not to perform cunnilingus on a menstruating woman? My significant other is particularly horny during her period and would love cunnilingus at this time. I am willing but curious.

I am curious about double penetration (two penises in one vagina). Because of the increased friction, even if both men are wearing condoms, is there more of a risk that the condoms would break?

I currently use NuvaRing for contraception. Because the ring slowly emits hormones into the body via the vagina, my partner and I are wondering whether he will have an unhealthy amount of contact with these hormones during oral sex. Thanks.

I am a well-adjusted late twenties male with a steady girlfriend. Lately, I have been increasingly fantasizing about various types of anal penetration. I have discovered that during masturbation, this brings me very intense pain/pleasure. Even though I think it may be satisfying to experiment with a vibrator or other objects inserted by my girlfriend, I find myself drawn toward trying the real thing (i.e., having anal sex with a penis). The problem is, I definitely do not consider myself homosexual and, in fact, the thought of the actual act with another man actually repulses me. Am I trying to have the real thing without going through a bisexual experiment or what?

1) Is it true that taking those Emergen-C packets or any other vitamin supplements can effect the effectiveness of your birth control pill?

2) I know antibiotics can lower the effectiveness of birth control, but can probiotics or prebiotics, such as a floral acidophilus FOS, also decrease effectiveness? I've been taking birth control pills for the past 10 years with no scares or baby bumps, and I don't want to wake up pregnant one day because I took a capsule that's supposed to be healthy! :)

I'm wondering if washing immediately and throughly after intercourse helps prevent pregnancy.

I have encountered a problem I never expected; my boyfriend is quite simply very large. I am unable to perform oral sex except for the first couple of inches due to the girth, and vaginal sex is not totally satisfying for him because he is too long and cannot fully penetrate without causing me significant pain. I've seen my doctor, and am reassured that there is physically nothing wrong with me — no infections or scarring, but am finding it difficult to come up with a solution. Any suggestions?

Some of the girls at my school talk about how their boyfriends got to first, second, or third base with them. I feel kind of left out because I don't know exactly what they are. Could you tell me what the bases are for girls and guys? I'd really appreciate it.

I am just curious about sex, and why is it such a turn on?? Is it the physical contact or sexual actions?? Or is it endorphins spreading through the body while it is happening??

If my partner and I have been monogamous for three years (and I was a virgin before we met) and my partner tested negative for the HIV virus (twice, about two years ago, with a six-month gap between the tests) is it safe for us to use a birth control method other than a condom? That is, are there still any STDs that my partner might have without knowing it, that we should be worried about, even though nothing whatsoever has seemed wrong with either of us for three years and my partner has had several regular annual physicals in that time?

Is it possible to get sick from oral sex, when your partner doesn't have any STD's? I've only ever had one partner, and recently I performed oral sex on him. Only ever since I have had a sore throat, and swollen glands. Is this related, or did I just pick up cold germs he was carrying?

After you have sex, how long should you wait till you do it again?

If a man is performing anal sex, can he actually feel his partner's waste products? Please answer because I read somewhere that the proper thing to do is perform an enema first and I can't believe this is true.